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Anthropic releases Claude Fable and Mythos 5.2 with benchmark results

AIAnthropic says it is releasing Claude Fable and Mythos 5.2 and that Fable beats Opus on large, long tasks such as rewriting a whole codebase. The accompanying table reports Fable 5.2 leading most listed benchmarks, including SWE-bench Pro at 93.0 and OSWorld 2.1 at 89.3, while Opus 5.5 scores higher on GDPval-AA and AA-Briefcase ELO. The author says he still often prefers Opus 5.5 for everyday work.
Felix RiesebergVerified on XOfficial
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We're releasing Claude Fable & Mythos 5.2! They're good models, I have some demos and tips for you.

Fable beats Opus on big, long tasks. Good examples are rewriting an entire codebase, creating an excellent first draft of a large artifact, or exploring ambiguous scenarios.

I expect to see it used to port a lot of stuff to Rust, support journalists in large-scale investigations, and help with research & science. I often still prefer Opus 5.5 for everyday work. Fable's got a big brain and thinks a little slower.

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Felix Rieseberg · x.comPublished · added here

Original title: We're releasing Claude Fable & Mythos 5.2! They're good models, I have some demos and tips for you.

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Anthropic / ClaudeAI codingModel releases